表面湿度 meaning in English

surface humidity
surface moisture

Method of test for surface moisture in fine aggregate
细集料表面湿度的试验方法
Standard guide for nuclear surface moisture and density gauge calibration facility setup
核表面湿度和密度量规校准设施装配的标准指南
Methods of test for total moisture content of aggregate and surface moisture in aggregate by drying
干燥法测定集料的含水总量及表面湿度的试验方法